ouch

from The American Heritage® Dictionary of the English Language, 5th Edition.

• interjection Used to express sudden pain or displeasure.
• noun A setting for a precious stone.
• noun A clasp or brooch, especially one set with jewels.

from The Century Dictionary.

• An exclamation expressing pain, as when one is suddenly hurt, as by a slight burn, a prick of a pin, etc.
• noun An ornament or jewel of the nature of a brooch or clasp; any jewel or ornament; specifically, a clasp used for a cope in place of the agraffe. Its use in the English Old Testament seems to be restricted to ‘setting,’ or ‘socket.’ Also owche.
• noun The blow given by a boar's tusk.
• noun A tumor or boil on the skin; a carbuncle.

from the GNU version of the Collaborative International Dictionary of English.

• noun A socket or bezel holding a precious stone; hence, a jewel or ornament worn on the person.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Alternative form of ouche.
• interjection An expression of one's own physical pain.
• interjection An expression in sympathy at another's pain.
• interjection A reply to an insult (frequently one that is tongue-in-cheek or joking).
• interjection An expression of disappointment.
• interjection slang, Australia, New Zealand, UK Expressing surprise at the high price of something.